1. Field of the Invention
The present invention relates to an ink supply device that supplies ink into a sub ink tank of a recording head unit, an ink-jet recording device having the ink supply device, and a method of supplying ink.
2. Description of the Related Art
In the ink-jet recording device that ejects ink drops on a recording medium such as a paper from recording heads on the basis of image information and records the image, there is such a configuration that mounts the sub ink tanks corresponding to each of the recording heads on a carriage to make the recording heads scan, in which there are various types of proposals as to the supply of ink into the sub ink tanks.
For example, Japanese Published Unexamined Patent Application No. Hei 6-238911 discloses an ink-jet printer as shown in FIG. 18, in which an ink tank 314 is disposed on one end of the shifting range of a recording head 312. The ink tank 314 has an ink supply outlet 318 formed at a position corresponding to an ink supply inlet 316 of the recording head 312, and has a bellow portion 320 formed on the middle thereof. And, as the recording head 312 returns to the home position, the ink supply inlet 316 of the recording head 312 is connected with the ink supply outlet 318 of the ink tank 314, and the recording head 312 is pressed to the ink tank 314 by a drive force of a drive motor not illustrated; thus, the bellow portion 320 of the ink tank 314 shrinks by this pressing force. Accordingly, the content volume of the ink tank 314 varies, and the ink inside the ink tank 314 flows into a common liquid chamber by way of the ink supply outlet 318 and the ink supply inlet 316. The ink tank 314 that once shrank recovers the original volume by the recording head 312 shifting and releasing the pressure, and by a self-restoring force of the bellow portion 320. AT this moment, a check valve 322 provided with the ink tank 314 opens, and the air equivalent to the volume of ink supplied into the recording head 312 flows into the ink tank 314 from an air intake 324.
However, in the construction in which the supply of ink is carried out by such pressurization, the supply of ink can take a comparably long time in some cases, which sometime lowers the efficiency of the ink supply.
In contrast to this, as shown in FIG. 19 and FIG. 20, the Japanese Published Unexamined Patent Application No. Hei 11-240180 discloses an ink-jet recording device that includes a first tank 354 provided with a recording head 352 and a second tank 356 to supply ink into the first tank 354. A switching hole 362 on a partition wall 360 that separates an ink chamber 358 of the first tank 354 from the recording head 352 can be opened and closed by a check valve 364; and as a differential pressure is produced, the switching hole 362 is to open. Supply of ink into the ink chamber 358 needs to couple a suction hole 366 with a suction cap 368, and thereafter drive a supply pump 370, thus decompressing the first tank 354. Next, a rubber seal 372 is made to advance by driving a reversible motor, and a needle 374 projected on the first tank 354 is inserted into the rubber seal 372, whereby the first tank 354 is connected with the second tank 356. Since the first tank 354 is in decompression, the ink is supplied from the second tank 356 into the first tank 354 by way of a tube 376.
However, in this construction, since the first tank 354 is not made to communicate with the atmosphere, the check valve 364 is required in order to prevent an ink leakage or air suction through a nozzle 378, due to a variation of the inner pressure, thereby making the structure complicated.
The present invention has been made in view of the above circumstances, and provides an ink supply device that permits supply of ink securely with a simple construction into a sub ink tank having an air communication hole, a method of supplying ink, and an ink-jet recording device provided with the ink supply device.
According to one aspect of the invention, the ink supply device possesses an ink supply unit provided in correspondence with a recording head unit including a recording head that ejects ink drops onto a recording medium on the basis of image information, and a sub ink tank provided with an air communication hole, storing the ink supplied to the recording head, which implements ink supply by a pressure reduction part reducing a pressure inside the sub ink tank; and a sealing part that at least permits sealing of the air communication hole while the ink supply unit is reducing the pressure inside the sub ink tank.
According to this invention, the sub ink tank that the ink is supplied into is provided with the air communication hole. This air communication hole softens a surge pressure variation inside the sub ink tank, accompanied with ejection""s of ink and/or environmental changes, and so forth, and prevents an unexpected ink leakage from the sub ink tank and a mixture of air (air suction from an ink discharging nozzle of the recording head, and creation of air bubbles inside the sub ink tank). Thus, the recording head maintains an optimum state for discharge of ink drops.
Also, since the ink supply device has the sealing part, at least the device is able to seal the air communication hole of the sub ink tank, while the ink supply unit is reducing the pressure inside the sub ink tank. In the sealing state, as the pressure reduction part reduces the pressure inside the sub ink tank, the air does not flow unexpectedly into the sub ink tank, and the ink flows securely into the sub ink tank, thus achieving a smooth ink supply.
In addition, the ink supply is carried out not by the pressurization but by the decompression inside the sub ink tank; and the ink supply can securely be carried out in a shorter time.
According to another aspect of the invention, the ink supply device further includes a displacement mechanism that displaces the ink supply unit in relation to the sub ink tank between a non-supply position where the ink is not supplied and a supply position where the ink is supplied, wherein the sealing part is provided with the ink supply unit, and it carries out sealing of the air communication hole, based on a displacement from the non-supply position to the supply position by the displacement mechanism.
That is, the ink supply unit is displaced by the displacement mechanism from the non-supply position to the supply position in relation to the sub ink tank. The ink supply unit is designed to supply ink into the sub ink tank at the supply position, where the ink is supplied into the sub ink tank.
As the ink supply unit displaces from the non-supply position to the supply position, by this displacement, the sealing part seals the air communication hole. In this manner, the utilization of the displacement of the ink supply unit simplifies the construction, and also secures the sealing of the air communication hole, interlocking with the ink supply operation into the sub ink tank.
Further, the sealing part is provided integrally with the ink supply unit.
Thereby, the ink supply device reduces the number of components, simplifies its construction to diminish the size, and reduces the manufacturing cost.
According to another aspect of the invention, the ink supply unit is provided with an air suction member and an ink supply member that are connected to the sub ink tank, and the sealing part is made to seal the air communication hole, after the air suction member and the ink supply member are connected to the sub ink tank.
Therefore, after the air suction member and the ink supply member are connected to the sub ink tank, the sealing part seals the air communication hole. In this state, as the air suction member sucks the air inside the sub ink tank, the ink flows into the sub ink tank from the ink supply member, resulting in supplying ink.
Now, in this series of operation, if the construction is such that the sealing part seals the air communication hole first, and then the air suction member and the ink supply member are connected to the sub ink tank, there will be apprehensions that a slight variation of pressure created during connection will not be absorbed, because the air communication hole is already sealed. In contract to this, in this invention, since the air suction member and the ink supply member are connected to the sub ink tank first, and then, the sealing part seals the air communication hole, a slight variation of pressure created during connection will be absorbed by the air communication hole that is not sealed.
According to another aspect of the invention, the ink supply member is provided with a valve mechanism.
This provision of the valve mechanism blocks up the ink supply member except during the ink supply, which precludes unexpected drying of ink, mixture of foreign matters into the ink, and so forth.
According to another aspect of the invention, a plural number of ink supply units are provided in correspondence with the plural recording head units, and the displacement mechanism displaces a specific one of the ink supply units and the sealing parts in relation to the corresponding specific one of the recording head units independently from the other ink supply units and sealing parts.
Since the plural ink supply units are provided in correspondence with the plural recording head units, for example, an ink-jet recording device capable of color image recording is able to supply ink into the sub ink tank of the recording head unit individually for each color.
According to another aspect of the invention, the pressure reduction part includes a suction pump.
The suction by the suction pump secures decompression inside the recording head unit in a short time.
According to another aspect of the invention, the ink-jet recording device includes any one of the foregoing ink supply devices, and a recording head unit including a sub ink tank into which the ink supply device supplies ink, provided with an air communication hole, and a recording head that ejects the ink supplied from the sub ink tank onto a recording medium on the basis of image information as ink drops.
In this ink-jet recording device, the ink supplied from the ink supply device into the sub ink tank of the recording head unit is ejected as ink drops onto a recording medium by the recording head, thereby forming an image on the recording medium. The sub ink tank is provided with the air communication hole, which eases a pressure variation due to ejection of ink and environmental changes, and so forth. Thereby, an unexpected ink leakage from the sub ink tank and a mixture of air into the sub ink tank can be prevented, and the recording head maintains an optimum state for discharge of ink drops.
And, since this ink-jet recording device includes any one of the foregoing ink supply devices, it is able to seal the air communication hole of the sub ink tank while supplying ink. In the sealing state, the decompression inside the sub ink tank by the pressure reduction part will preclude an unexpected flow of air into the sub ink tank through the air communication hole; and accordingly, the ink securely flows into the sub ink tank. Thus, the ink is supplied by means of the decompression inside the sub ink tank, not by the pressurization, and a secure ink supply can be achieved in a shorter time.
According to another aspect of the invention, it is preferable that both a supplying connection portion to which the ink supply member is connected and an sucking connection portion to which the air suction member is connected, in the sub ink tank, include a valve mechanism.
Therefore, the valve mechanism is able to block up the supplying connection portion and the sucking connection portion, except while supplying ink into the sub ink tank, whereby unexpected evaporation of ink and leakage of ink and so forth can be prevented.
According to another aspect of the invention, the method of supplying ink into a sub ink tank provided with an air communication hole, in which the ink supplied to a recording head is stored includes a connection step of connecting an air suction member and an ink supply member to the sub ink tank, the air suction member capable of sucking air from the sub ink tank and the ink supply member capable of supplying the ink into the sub ink tank; a sealing step of sealing the air communication hole by a sealing part, after the connection step; and an suction step of sucking the air from the sub ink tank by the air suction member, after the sealing step.
That is, at the connection step, after the air suction member and the ink supply member are connected to the sub ink tank, at the sealing step, the sealing part seals the air communication hole. Therefore, if there is a slight variation of pressure created during connection, the variation of pressure will be absorbed by the air communication hole that is not sealed.
Thereafter, at the suction step, the air suction member sucks the air from the sub ink tank. Thereby, the ink flows into the sub ink tank through the ink supply member. Since the sealing part seals the air communication hole, the ink can be supplied securely into the sub ink tank in a shorter time.
In addition, the sub ink tank into which the ink is supplied has the air communication hole, which softens pressure variations inside the sub ink tank resulting from the discharges of ink and environmental changes and so forth. Thereby, an unexpected ink leakage from the sub ink tank and a mixture of air into the sub ink tank can be prevented, and the recording head maintains an optimum state for discharge of ink drops.
According to another aspect of the invention, the method of supplying ink further includes a sealing release step of releasing the sealing of the air communication hole by the sealing part, after the suction step; and a disconnection step of disconnecting the air suction member and the ink supply member from the sub ink tank, after the sealing release step.
Thus, after the ink supply is completed, first the sealing of the air communication hole is released at the sealing release step, and next at the disconnection step, the air suction member and the ink supply member are disconnected from the sub ink tank. Therefore, if there occurs a slight pressure variation during disconnection, this pressure variation will be absorbed, because the air communication hole is already opened (not sealed) at this moment.